iOS: Facebook's Messenger app used to be a mere extension of Facebook's messaging functionality, but as of today Facebook added a handy new feature for US users: free voice calling.

Now, when you open up Messenger and tap on a friend, you'll see a new button entitled "Free Call." With it, you can give them a ring and, if they have the Messenger app as well, you'll be able to talk to them over Wi-Fi or cellular data without using up any minutes. Of course, you could just use Skype, but this is just one more option for your friends that maybe don't have Skype accounts already.

Facebook Messenger is a free download for iOS, and if you already have the app, you don't need to upgrade to get the new feature.